Personally for me .3. I look for a few things~
1. An awesome name to start things off, a nice catchy name .3. (none of them on forums I like, that's why I still haven't joined one lol)
2. A social network, I think this is pretty normal in guilds. Can't have guild members that don't say anything to each other .3.
3. Advice and guidance to other fellow members especially if they're new to the game. Things like defence tests, arena team advice, event help, ally recruitment, help members find specific units etc.
4. Guild Events/Competitions(not sure, but putting it here anyway), especially in events that you don't really care about or in during cooldown. Of course having events are somewhat limited due to limited things you can do in game .3.' But things like making a guild banner or artwork or something of the like is possible.